ABB Relion 670 Series Applications Manual page 163

1MRK 505 370-UUS Rev. K
A1
t=0
The fault
occurs
ANSI05000205 V1 EN-US
Figure 91:
where:
t=0
t=t
1
t=t
2
t=t
3
t=t
4
To ensure that the overcurrent protection at IED A1 is selective to the overcurrent protection at IED B1,
the minimum time difference must be larger than the time t
protection operation time, breaker opening time and protection resetting time. Therefore a safety margin
has to be included. With normal values the needed time difference can be calculated according to
Equation 32.
D ³
t 40
EQUATION1266 V1 EN-US
where it is considered that:
the operate time of overcurrent protection B1 is 40 ms
the breaker open time
the resetting time of protection A1
the additional margin
7.2 Four step single phase overcurrent protection PH4SPTOC
(51)
Busbar protection REB670
Application manual
51
t=t t=t
1
Protection Breaker at
B1 trips B1 opens
Sequence of events during fault
is when the fault occurs
is when protection IED B1 and protection IED A1 start
is when the trip signal from the overcurrent protection at IED B1 is sent to the circuit breaker.
is when the circuit breaker at IED B1 opens. The circuit breaker opening time is t
is when the overcurrent protection at IED A1 resets. The protection resetting time is t
+ + +
ms 100 ms 40 ms
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B1
51
t=t
2 3
Protection
A1 resets
. There are uncertainties in the values of
3
=
40 ms 220 ms
is 100 ms
is 40 ms and
is 40 ms
Section 7
Current protection
Feeder
Time axis
en05000205_ansi.vsd
- t
3 2
- t .
4 3
(Equation 32)
SEMOD127812-1 v2
157